The present invention relates to orthopaedic methods and devices for the gradual modification of bones or correction of bone deformities. In particular, the present invention relates to a variety of bone reshaping devices configured to perform procedures, including the lengthening of a bone, the shortening of a bone, the healing of a fracture, the changing of a bone angle, the rotation of a bone, the adjustment of the curvature or torsion of a bone, the realignment or repositioning of a joint or a vertebra, the reforming or supporting of the shape of the spinal column, or combinations thereof, all of which are considered species of “reshaping” as used herein. More specifically, the present invention relates to methods and systems concerning bone reshaping devices that can be externally adjusted based on measured parameters indicative of biological conditions.
External fixation devices, adjustable in length and angular attitude, are commonly utilized for correcting certain angular and longitudinal defects of long bones of limbs. Such fixation devices essentially comprise clamps which hold groups of bone screws inserted in the portions of the bone affected by defects, such clamps being slidably mounted on elements or guides longitudinally positionable externally to the limb to be treated.
The correction is normally carried out gradually with the aid of compression/distraction devices which act on the mobile clamps while the bone callous regenerates itself permitting its manipulation until the desired correction is obtained.
For example, in limb lengthening, the bone is commonly surgically divided into two segments, and wires and half pins are inserted into bone segments above and below the surgical hone cut and are attached to rings of a rigid framework interconnected by struts or telescopic connection rods. The rigid framework is used to gradually push the two bone segments apart longitudinally over a period of time (e.g., one millimeter a day). This allows the bone to gradually form in the gap between bone segments created by this distraction technique. Once the desired amount of lengthening is achieved 5-6 cm), the external apparatus is stabilized into a fixed position and left on the bone segments until complete mineralization of the newly formed bone occurs 3-6 months, depending on the nature of pathology and amount of lengthening).
Similarly, in deformity correction, the bone is surgically divided usually at the apex of the deformity) into two segments, and wires and half pins are inserted into bone segments above and below the surgical bone cut and attached to rings of a rigid framework. Opposite rings of the rigid framework are connected together by threaded rods with attached uni-planar or multi-planar hinges and angular distracters that are used to gradually push the two bone segments apart angularly over a period of time.
The use of such external fixation devices can present certain disadvantages. The external fixator can be unwieldy, painful for the patient, and also subjects the patient to the risk of pin track infections, joint stiffness, loss of appetite, depression, cartilage damage, and other side effects. Having the external fixator in place also delays the beginning of rehabilitation. In some circumstances, the visibility of the external fixator can lead to patient embarrassment or insecurity.
In response to these shortcomings, the art developed implantable devices that could be positioned under the skin and/or in bones. These devices were designed to correct bone deformities by applying force to bones, including compressive forces to promote healing, distractive forces to promote lengthening, and angular forces to change the angle/curvature of bones. Some desirable aspects of these implantable devices were that they could apply steady forces over defined periods of time, did not have external wires or rods that could bother the patient or cause pain, had reduced risks of infections, and were not readily visible.
Yet, even these implantable devices could have limitations as well in some cases. For example, because of their location under the skin, some implants could be difficult for care providers to observe, monitor, and adjust. As such, additional surgical procedures would sometimes be performed to incrementally adjust an implant as therapeutically required. The additional surgical procedures exposed patients to increased risks of infection, longer healing times, injury, and increased pain.
In other cases, even where adjustments to implants could be made through the skin, the therapeutic effects of the implant could be less than optimal. Under-application of force could lead to poor bone reformation and/or require longer recovery times. Over-application of force could lead to injury, further bone deformation, and also longer recovery times. Moreover, frequent visits to see a practitioner for adjustments could be time consuming or otherwise inconvenient for a patient.
Thus, notwithstanding the efforts of the prior art, there remains a need for an improved technology for controlling implantable bone reshaping devices in order to improve their performance and efficacy.